QT about "Fatal error:QApplication:No such file or directory" error resolution

"Fatal error:QApplication:No such file or directory" error occurred due to QT4 compatibility issues when building QT Engineering

The solution is also simple:
In the project. Pro File: Add:
QT + + Core GUI widgets

If it is not yet available, replace # include <QApplication>
#include <QtWidgets/QApplication>

For example:

#include <QtWidgets/QApplication>   <QtWidgets/QLabel>int main (int argc, Char *argv[]) {     qapplication app (ARGC,ARGV);      New Qlabel ("Hello lover Snow ");    Label, Show ();     return app.exec ();}

QT about "Fatal error:QApplication:No such file or directory" error resolution